Wednesday, February 29, 2012

Today was probably the maximum crowd at the APS meeting. Saw a number of talks and had lots of conversations. One particularly interesting talk was about variations on this result. In condensed matter we've become used to the idea of "photonic band gap" or "photonic crystal" materials, systems where a spatially periodic pattern of dielectric contrast (e.g., glass vs. air) results in optical properties that mimic the electronic properties of crystals: bands (energy ranges) where light can propagate freely, and (photonic) band gaps, where light is reflected and can't propagate. This talk was about weird "hyperuniform" disordered dielectric structures that nonetheless have a complete photonic band gap (in all directions) in 2d, and the fact that by introducing voids and defects in these systems, it's possible to make very selective and directional waveguides. I need to read more about the math behind this. The experiment uses microwaves rather than visible light, meaning that it's possible to build such structures by hand using sapphire plates and rods on the centimeter scale.

The Buckley Prize session was also very good, though I missed talks in the middle. Very crowded, particularly for Charlie Kane's talk. That one would have been fun if it'd been a full hour - it felt like he had to abbreviate some of the discussion to fit into the 30+6 minute slot.

Another highlight this afternoon was the big Kavli session about the mesoscale. The lead talk was from Bob Laughlin, who is always entertaining. He focused on the big open question of whether there are laws that emerge in biology. By his definition, a law is a quantitative relationship between measured parameters that always holds. Some laws are (apparently) fundamental, like the force between two point charges in vacuum. Others are emergent, like the relationship between stress and strain in elastic media, or the Navier-Stokes equations that govern hydrodynamics. In the emergent situation, emergent laws hold when the system is sufficiently macroscopic. Laughlin's big question is, are there universal quantitative relationships that emerge in biological systems (beyond the trivial ones already mentioned, like elasticity being useful for describing cell membranes)? He says that there are hints all over, but it's very hard to do the definitive experiments because biology is just so complicated and our experimental tools are comparatively invasive and crude. When asked to describe biologists in one word, he said "frustrated".

The talk also put forward two definitions of what condensed matter physicists do, both of which are very good. Via Laughlin, Michael Fisher says: "Our job [as condensed matter physicists] is to discover and understand the phases of matter and the transitions between them." Laughlin himself says: "Our job [as condensed matter physicists] is to discover the emergent laws of nature, and hand them to engineers so that they can be put to use." Good stuff. On a lighter note, I realized partway through the talk that every now and then it's entertaining to imagine Laughlin's words as if said by William Shatner. "We trust the emergent laws of rigidity and hydrodynamics...to make an airplane...that can go up to 35000 ft...and not...explode!"

As I am every year, I was again somewhat shocked by how many people come to this meeting. The attendance just keeps going up, and unfortunately that usually correlates with a decrease in the utility of the average talk. For PIs, the meeting is more about interacting with each other, vendors, potential hires (postdoc or faculty) than it is about actually learning things from talks.

I did actually learn a few things in talks yesterday, though, even without going to sessions on the super hot topics (graphene, topological insulators).

I went to the first half of an interesting session about presenting science to the public, something that I think is very important. The first talk was about a theater group collaborating with MIT, with a history of developing plays based on physics (including Einstein's Dreams by Alan Lightman). Here, free of charge, are my suggestions for other play possibilities: The birth of Silicon Valley, emphasizing that in many ways it stems from the fact that Shockley was such a micromanager that no one could work with him; the genesis of the hydrogen bomb, emphasizing that Teller's difficult personality delayed the development of his much-loved "super" by at least two years, because very few people could work with him. (Sense a theme?). The second talk was by Odd Todd Rosenberg, an animator who works with Robert Krulwich of ABC and NPR science fame. The cartoons were funny and informative, though the discussion raised the recurring issue of oversimplification and inaccuracy in broadly popular marketing of science.

I also went to a very strong session all about vanadium dioxide, which was quite informative. Sounds like many people in the strong correlations game are starting to look very hard at ionic liquids for gating. Here the major challenge is whether people are inadvertently (or advertently) doing chemistry on their structures.

There was also a very fun talk by Hongkun Park of Harvard, who discussed "quantum plasmonics" - trying to couple individual emitters and absorbers to plasmonic waveguides. For example, you can have a GaAs nanowire touching a silver nanowire. When biased appropriately the GaAs emits photons which couple strongly into guided plasmon modes of the Ag wire, propagate as plasmons, and are then generate photocurrent at a junction with a Ge nanowire at the other end of the silver wire. This is a "dark plasmonic" circuit, with light being generated, propagated, and detected on the subwavelength scale. Cool stuff.

Monday, February 27, 2012

For an organization so deeply ingrained with technology, the American Physical Society has some surprising issues. For example, as I type this, I'm downloading the complete program to the March Meeting at the blazing pace of 5 kB/s, and that's not limited by my connection. For another example, once again the APS has released a mobile app that contains the whole program and is supposed to be searchable. Unfortunately, the user interface on the app (at least the ipad version) is dreadful, unintuitive, and creepingly slow. Geez.

Thursday, February 23, 2012

When historians of science look back on the whole OPERA superluminal neutrino discussion, one way or the other, there are going to be a number of lessons to draw from the experience about how science and science journalism function in the early 21st century.

Yesterday, with "BREAKING NEWS" headlines, Science magazine proclaimed: "Error Undoes Faster-Than-Light Neutrino Results". In that article, "according to sources familiar with the experiment", the whole timing discrepancy for the neutrinos is traced to a bad fiber optic connection to a GPS receiver. The claim from that article is that "After tightening the connection then remeasuring the time it takes data to travel the length of the fiber, researchers found that the data arrive 60 nanoseconds earlier than assumed." Since that's the critical amount by which the neutrinos allegedly arrived too soon for special relativity, that would seem to be the end of the story. Embarrassing for OPERA, but case closed, right? T

Wrong. First, on its face, this seems weird - no one is quoted by name, and the idea that a loose fiber coupling could contribute 60 ns in timing is pretty odd (since that would correspond to something like 18 m of free space optical path). At minimum, the description above must be garbled.

Moreover, the actual email from the CERN director does not say this at all. Rather, it says that OPERA has identified two outstanding issues, one involving an oscillator that provides timestamps for the GPS synch, and an optical fiber connector that brings the GPS signal to the OPERA master clock. The former issue could make the neutrino timing problem worse, in fact. Moreover, the message says explicitly that they are going to take new measurements in May to check these issues. That seems to flatly contradict the news article claiming that they've already done tests. For a detailed discussion, see Matt Strassler's excellent blog here.

Bottom line: as I've said before, the superluminal neutrino result is almost certainly wrong, but the jury is still out on how and why, despite what the Science news blurb says. Believe me, if they knew for sure how this stood, they'd end it with a definitive statement, not stretch this out 'til May.

UPDATE: Prof. Strassler has the best write-up of this, based on detailed reporting from the European press. Because of two different, subtle technical flaws, the uncertainty in the OPERA results is bigger than the 60 ns timing discrepancy, meaning (1) the result is not in contradiction w/ special relativity (big surprise), and (2) they need to run with fresh data and the problems rectified to make any more definitive statement.

Sunday, February 19, 2012

"Spontaneous symmetry breaking" is a profound idea from condensed matter physics that has been adopted with a vengeance by the high energy physics community. Let me give an example. The laws of physics are, as far as we know, "translationally invariant" - they don't depend on our location in space, and if we move a little bit nothing happens to those laws. That's translational symmetry (and it turns out it's deeply connected to conservation of momentum, but that's another story). However, if we consider atoms moving about in space and worry about what configurations they like to adopt, the atoms tend spontaneously to adopt a lower symmetry state. For example, atoms will often arrange themselves into a regular spatial periodicity that we call a crystal structure. Now instead of space being continuously translationally invariant, the arrangement of atoms has a discrete translational symmetry - the arrangement of atoms reproduces itself if translated by integer multiples of a particular lattice parameter.

This week, two papers (here and here) appeared, from (the polymath) Frank Wilczek's group at MIT. Wilczek is one of the rare theorists who moves seamlessly between condensed matter and high energy theory. In these papers, the idea of "time crystals" is discussed. As science fiction-y as this sounds, it's real, but it is an application of this idea of spontaneous symmetry breaking, not some exotic Doctor Who concept. In analog with the above discussion, as far as we know, the laws of physics are also invariant under translations in time. The idea in these papers is that dynamical systems may spontaneously break that continuous translational invariance, and exhibit discrete time translation invariance instead. That means that dynamical systems may spontaneously take on periodicity in time! I need to read the second paper in detail soon - the quantum versions of these ideas seems very deep....

Friday, February 17, 2012

There's a new meme floating around the web these days. Here's an example:

I'd like to propose a contest for a version of this for "Physicist", or even better, "Condensed Matter Physicist", "Nanotechnologist", or something along those lines. Put up some nominations (links in the comments), and I'll have voting to pick a winner.

Tuesday, February 14, 2012

Two semi-related topics have come to mind lately. First, this post by the FSP caught my attention, regarding "citation circles", where a sub-community within a scientific discipline agree to cite each others' work. I've heard of such things, and there's nothing inherently wrong there as long as the citations are relevant and don't consciously omit other equally relevant papers. Still, I never considered this practice to have too much impact. Back when I was in grad school, I'd heard of something that is equally fine ethically, and perhaps more important to progress in the long term: the timely reviewing circle - a group of scientists who agree to respond promptly to invitations to review one anothers' work. This is not a matter of conspiring to give positive reviews, but an agreement to get manuscripts through the review process quickly. Imagine if certain "Letters" journals were actually speedy!

The second topic is the idea of trying to influence the selection of referees. Of course, under many circumstances you as an author can suggest possible referees for scientific papers or grant proposals. Let's call that a first-order influence. It's a way of making sure that the editors can get the paper out to technically knowledgeable people in a specialty. (I've been told by multiple editors that authors who try to suggest "friendly" referees often do themselves more harm than good, because those suggested reviewers are often more harsh than randomly selected peers.) Recently I learned about a "higher-order" approach: avoiding citing the work of potentially hostile reviewers, under the assumption that the editor/program officer often gets referee ideas from the reference lists. I am very skeptical that this approach could matter in a statistically significant way.

Tuesday, February 07, 2012

I really got a kick out of this video, and this one (some overlap), of President Obama at the White House Science Fair. See here for a press description, and here for the White House's own page on the matter. Note that Bill Nye was there - how cool is that? It's great to see a President who uses a bit of the prestige of the office to shine a spotlight on the importance of science education.

On an unrelated note, on the way home from work today I heard this story on NPR, about the challenges of nonprofits, specifically charities, that fund science research. There is a tendency for those charities to shy away from politically controversial topics (e.g., human embryonic stem cells) because charities don't want to risk alienating any potential donor. It is an interesting set of issues. Charities are of course not obligated to fund any specific thing. My sense is that one clear ethical line is that charities should be open and honest about what they do and don't support. No hidden agendas. If you don't want to fund something, just say so clearly, so that there's no "buyer's remorse" from donors who feel mislead.

Saturday, February 04, 2012

Many people online have heard about and commented on this sad story. An assistant prof in molecular biology at Case Western published a paper in the "journal" Life that purported to explain essentially all of creation in terms of "gyres", some hand-wavy vortex-like entities. As the always provocative PZ Myers points out, the paper itself is basically word salad - it sounds disturbingly like the writings of someone having real mental health issues. The fact that it got published shows what a sham some journals are. I suspect that many of my academic peers have gotten email invitations to serve on the editorial boards of pay-to-publish journals. Several members of the board at Life have apparently resigned over this mess. However, this sad affair does raise some points worthy of consideration:

1) How did the media services office at CWRU actually end up putting out a big press release about this? Do they simply have no judgment whatsoever about content? I mean, could any professor ask them to put out a press release about anything, and it wouldn't be filtered at all before going out to the media?

2) Do aggregators like Eurekalert and Physorg serve as a positive influence overall? Yes, they help get science news stories out to the wider media, but don't they have some responsibility to make sure that they aren't just a conduit for junk? Surely they weren't originally intended just to be redistributors of unedited press releases.

3) What are the responsibilities of academic authors, department chairs, deans, etc. when it comes to press releases? Lord knows, I would not want to have to get permission from a higher-up at my university to speak my mind or point out a cool new result. However, it doesn't necessarily do anyone a lot of good if people put out press releases and have a media blitz for every little result, let alone the occasional whacko idea. While universities generally like media mentions of their researchers, CWRU can't be happy about this situation.

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About Me

My professional background: After an undergrad degree from Princeton in mechanical and aerospace engineering, I went to grad school at Stanford and got a doctorate in physics. Following a postdoctoral appointment at Bell Labs, I moved to Rice University and established a research program in experimental condensed matter physics, with a particular emphasis on nanoscale science. If you're interested in this stuff, please think about buying my book - it's a page-turner, and you'll want to finish it before the HBO miniseries spoils the ending. (That last part was a joke.) I blog regularly about science at Nanoscale Views. As should be obvious to pretty much everyone, anything I say there or here are my personal views, and in no way are official opinions of Rice University or its Department of Physics and Astronomy.